Fluoropolymer films have long been used as a protective and decorative overlay for a variety of substrates such as metal, wood, and thermoplastic and thermoset polymers. With its excellent chemical resistance and weathering properties, a thin layer of fluoropolymer film can protect less durable substrates from damage in both exterior and interior use. In recent years, manufacturers of automobiles, recreational vehicles, sports craft and industrial and farm equipment have begun using fluoropolymer film structures to surface selected parts of vehicles and equipment in lieu of paint. Single layer polymer film and multilayer polymer films have been used.
Fluoropolymer films such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) polymers and copolymers and blends of acrylic polymers and PVDF are often used in the form of a preformed film to provide the protective surface layer. Such films are often applied to a thermoplastic substrate to form a laminate which is then subjected to a thermoforming operation. A wide number of thermoplastic substrates are desirable for use such as polyolefins, polyesters, nylon, ABS, etc. More recently, fluoropolymer films have been recognized as an important component in photovoltaic modules due to their weather resistance, UV resistance, and moisture barrier properties. When fluoropolymer such as PVF is used as a backing sheet to the module, its properties significantly improve module life, allowing module warranties of up to 25 years. Fluoropolymer backing sheets are frequently employed in the form of laminate with polyethylene terephthalate (PET) films, typically with the PET sandwiched between two fluoropolymer films.
However, laminates of preformed fluoropolymer films on polymeric substrates having a bond which will not delaminate after years of outdoor exposure are difficult to make. Prior art systems such as U.S. Pat. No. 3,133,854 to Simms, U.S. Pat. No. 5,139,878 to Kim et al., and U.S. Pat. No. 6,632,518 to Schmidt et al. describe primers and adhesives for preformed films that will produce durable laminate structures. However, these processes require the application of at least one adhesive layer, or both a primer and adhesive layer, prior to the actual lamination step. The lamination step then requires the application of heat and pressure to form the laminate. Therefore, prior art laminates using preformed fluoropolymer films are expensive to manufacture and/or require capital intensive equipment. Because preformed fluoropolymer films must have sufficient thickness to provide strength for handling during manufacture and subsequent processing, the resulting laminates may also incorporate thick expensive layers of fluoropolymer, i.e., thicker than are necessary for an effective protective layer.